An attendee reflects on the tragedy of Wednesday's attack during a candlelight vigil in San Bernardino, Calif., Dec. 3. California shooter Syed Rizwan Farook and Tashfeen Malik his wife and mother of his 6-month-old daughter, were killed in a shootout with police after the couple opened fire at the Inland Regional Center social services agency in the city of San Bernardino, killing 14 people.

The woman involved in last Wednesday's shooting in San Bernardino, Calif., entered the United States with a K-1 visa – also known as a "fiancé visa," raising questions on whether the vetting process is extensive enough to detect people who might be harboring anti-American sentiments.

Programs for welcoming foreign nationals into the country have been under heightened scrutiny following the deaths of 130 people in the Nov. 13 terrorist attacks in Paris. Refugee settlement programs and the US visa waiver program have become particular focal points for politicians and law makers looking to seal up holes in the immigration process that could allow entry to potential terrorists. But the FBI's announcement that the shooters who killed 14 people after storming a health department Christmas party at a facility for developmentally disabled individuals had been radicalized for "quite some time" has prompted officials to take a critical look at the K-1 visa program as well.

Tashfeen Malik, who had been living in Pakistan and visiting family in Saudi Arabia had passed several government background checks and entered the US in July 2014 with Syed Farook, a US citizen whose family was originally from Pakistan.

According to State Department figures, out of 9.9 million visas issued in fiscal 2014, just 35,925 — roughly 0.3 percent — were fiancé visas.

Authorities said on Monday that they are reviewing the program, though it is not clear what changes were being considered.

Officials from the Department of Homeland Security and the State Department are reviewing the fiancé visa program "to assess possible program enhancements," DHS spokeswoman Marsha Catron told the Associated Press. The Obama administration and lawmakers are also reviewing the visa waiver program, which allows most citizens from 38 countries to travel to the United States without applying for a visa. Pakistan, however, is not on the visa waiver list.

Investigators said Friday that the Pakistani-born Malik, had pledged allegiance to the Islamic State and its leader under an alias account on Facebook just moments before she and her husband, Mr. Farook, opened fire at the Inland Regional Center social services agency killing 14 people.

Malik and Farook were killed in a gun battle with the police on Wednesday, leaving behind a 6-month-old daughter.

K-1 visa applicants are already subject to numerous background checks prior to admittance. Through the standard procedure, applicants are subject to a vetting process that includes at least one in-person interview, fingerprints, checks against US terrorist watch lists and reviews of family members, travel history and places where a person has lived and worked.

But there are concerns about whether the process is stringent enough.

Homeland Security Secretary Jeh Johnson says it is too soon to say whether there was a failure on the government’s part to detect Malik’s alleged sympathies according to Secretary Johnson.

"That assumes, and this investigation is still under way, that there were flags that were raised or should have been raised in the process of her admission to the United States, and I am not prepared to say that and I'm not prepared to make that declaration," Johnson said.